What Is a Thyroid Ultrasound (USG)? Why Is It Requested and How Is It Performed?

The thyroid gland is an important organ that produces many hormones. Various diseases can affect it, some with potentially serious consequences.

We therefore sometimes use ultrasound (USG) to image the thyroid gland. This imaging method diagnoses conditions such as cancer and cysts, but further tests may sometimes be needed, such as a needle biopsy when cancer is suspected.

This article explains what ultrasound is, the thyroid gland's function and some conditions that can be detected with thyroid ultrasound. It also outlines the limitations of a typical thyroid ultrasound examination. Finally, it answers some frequently asked questions about thyroid ultrasound.

What Is Ultrasound?

Ultrasound is a type of medical imaging that doctors may also call ultrasonography. This technology uses very high-frequency sound waves to create images of the inside of a person's body. In some cases, it may allow doctors to make a diagnosis without more invasive techniques such as a biopsy.

Doctors most commonly use ultrasound to detect problems involving the thyroid gland. This imaging method is safe, convenient and cost-effective.

• Related topic: What Is a Thyroid Biopsy? Which Nodules Should Be Biopsied?

What Does the Thyroid Gland Do?

The thyroid is a gland in the neck. Its function is to produce a range of hormones, including thyroxine (T4) and triiodothyronine (T3). These hormones act as messengers in the bloodstream and tissues, affecting various bodily processes.

The thyroid produces hormones with many different effects, from regulating the body's metabolism to making new proteins. Thyroid hormones are also important for healthy fetal development, modulation of wakefulness and reproductive functions.

Why Is a Thyroid Ultrasound Requested?

Doctors request thyroid ultrasound to help detect thyroid diseases. Thyroid ultrasound may provide evidence for or against the following conditions:

• Goiter: This swelling of the thyroid gland can produce a lump or mass in the neck or throat.
• Graves' disease: An autoimmune condition in which the immune system attacks healthy thyroid cells.
• Lymphoma: Lymphoma is cancer of the lymphatic system, which forms part of the immune system.
• Lymphadenopathy: The term used for swollen lymph nodes.
• Thyroid cancer: Doctors may use ultrasound to predict whether growths in the thyroid gland are cancerous.

Thyroid ultrasound can also detect benign thyroid abnormalities. Doctors interpret ultrasound images carefully and may recommend further tests, such as scintigraphy, additional blood tests and biopsy, to confirm a diagnosis.

How Is a Thyroid Ultrasound Performed and How Should You Prepare?

Patients generally do not need to prepare for ultrasound scans. However, your doctor will tell you about any preparatory steps you need to take.

An ultrasound scan typically takes 20-30 minutes. It can be performed in a radiologist's office, a clinic or a hospital.

After applying a water-based gel around the neck and throat, the radiologist moves the USG probe (transducer) over the front of the neck. The probe emits and receives ultrasound waves. A computer then analyzes the waves to create an image of the thyroid gland and surrounding tissues. At the end of the procedure, the water-based gel is easily wiped away with a tissue.

Limitations of Thyroid Ultrasound

Thyroid ultrasound can help doctors diagnose various thyroid-related conditions. Sometimes, however, these tests need to be supplemented with other diagnostic procedures. This approach may help rule out false-positive and false-negative results.

Although ultrasound can detect thyroid nodules, it cannot always determine whether they are cancerous. Other diagnostic methods are therefore necessary.

Nevertheless, ultrasound is very useful for thyroid diseases.

When USG reveals a thyroid nodule, doctors may decide to perform a biopsy. This involves using a thin needle to remove part of the nodule, which then undergoes laboratory testing. If a biopsy is performed, it is also done under USG guidance.

Other tests that may help detect thyroid cancer include:

• Radioactive iodine scan
• CT (computed tomography) scan
• Magnetic resonance imaging
• Blood tests

Related topic: Which Patients Should Receive Radioactive Iodine Therapy After Thyroid Cancer Surgery? 

Summary

Thyroid ultrasound scans are a safe and effective way to produce images of the thyroid gland. They can help doctors diagnose a variety of thyroid-related diseases.

However, this imaging technique can produce both false positives and false negatives. Doctors may therefore sometimes supplement thyroid ultrasound with other diagnostic tests. Additional tests will always be necessary to confirm a cancer diagnosis.